This invention relates to a workpiece locating fixture and particularly to one useful for locating the center of an internal profiled surface such as internal gear teeth or splines.
Expanding arbors are used for holding and rotating workpieces and have a plurality of expanding members which engage an inside surface such as a bore. These devices position the workpiece relative to the internal surface for measuring concentricity or other dimensional relationships and for positioning a workpiece during machining operations. Several examples of such a device are described in U.S. Pat. No. 3,100,117. These devices have a number of balls which are supported by confronting and movable tapered surfaces which enable the radial positioning of the balls to be varied by moving the tapered surfaces toward or away from each other. The devices according to that patent are useful for locating a workpiece having a smooth surfaced bore, but are unsuited for positioning workpieces having internally profiled surfaces such as internal gear teeth or splines since the expanding balls may not properly engage with the profile features due to their diameter and shape. Expanding arbors of the above type cannot be modified to accomodate certain profile shapes since the diameter of their expanding balls is dictated by the configuration of the tapered surfaces and the range of radial expansion desired.
In view of the foregoing, it is an object of this invention to provide an expanding arbor device capable of locating components having profiled internal surfaces which is not subject to the disadvantages of devices according to the prior art.
In addition to testing concentricity of workpieces, their axial dimensions are often of significance. The above-mentioned U.S. patent provides a means for establishing the concentricity of an internal surface, but does not have means for simultaneously axially locating the workpiece. For some applications, there is a need for such simultaneous location of a workpiece. Accordingly, it is a further object of this invention to provide an arbor for locating a workpiece with respect to its concentricity and axial dimensions.